This invention relates to rotating disk data storage apparatus in general and, in particular, to the improved space saving configuration of a flexible printed circuit board, to which a magnetic data transducer or head is electrically connected, on a planar flexure seat resiliently supporting the transducer. The invention represents an improvement of the copending U.S. patent application Ser. No. 875,454 filed Apr. 29, 1992, by Nagase under the title of "Improved Connection of Transducer Leads to a Printed Circuit Board in Rotating Disk Data Storage Apparatus" and assigned to the assignee of the instant application.
The three and a half inch flexible magnetic disk and disk drives for use therewith have won widespread commercial acceptance. The disk is rotatably housed in a generally flat, boxlike envelope of relatively rigid plastic material, complete with a metal made sliding shutter, to make up a disk cassette. The envelope has a pair of apertures of rectangular shape to expose radial portions of the opposite sides of the disk. The sliding shutter also has a pair of apertures of approximately the same shape and size as the envelope apertures, which shutter apertures come into and out of register with the envelope apertures with the movement of the shutter relative to the envelope. The magnetic disk has a rigid hub of magnetic sheet metal attached centrally thereto. The hub has defined therein a central opening of square shape and an eccentric opening of rectangular shape.
When positioned in the associated disk drive, the magnetic disk has its central hub placed on a turntable which is much less in diameter than the disk. The turntable has a permanent magnet mounted thereto for attracting the disk hub. Disposed centrally on the turntable, a spindle engages in the central opening in the disk hub for centering the disk on the turntable. A drive pin is disposed eccentrically on the turntable for driving engagement in the eccentric opening or slot in the disk hub, imparting the rotation of the turntable to the disk.
The disk drive has a pair of magnetic data transducers or read/write heads for data transfer with the opposite sides of the disk through the registered envelope and shutter apertures. One of the transducers is mounted via a planar flexure seat on a carriage movable across the annular, concentric data tracks on the disk. The other transducer is mounted via another planar flexure seat on a load arm which is hingedly mounted to the carriage for pivotal motion toward and away from the disk.
Usually, with this type of disk drive, the lead wires or pins of each transducer were soldered to a conductive pattern on a flexible printed circuit board disposed on that side of the associated flexure seat opposite to the one on which the transducer was mounted. Each soldered joint rose to a height of 0.3 to 0.6 millimeters. Negligible as it might seem, the solder of such height represented a serious inconvenience in reducing the thickness or height of the disk drive to an absolute minimum, as is the trend today.
It might be contemplated to dispose the flexible printed circuit boards on the same side of the flexure seats as the transducers. This solution is objectionable because then the circuit boards might contact the envelope of the disk cassette. Particularly in the case where the envelope has the metal made sliding shutter, the conductive patterns on the circuit boards might be thereby short circuited to the destruction of the transducers.
Another solution is found in Nagase U.S. patent application Ser. No. 875,454, supra. In this application each printed circuit board, generally disposed on that side of the flexure seat opposite to the side where the transducer was mounted, was shaped to include a pair of end portions which were bent and folded through openings in the flexure seat onto the same side as the transducer. The transducer leads were soldered to these folded end portions of the circuit board. Consequently, the solder itself represents no bar to the reduction of the thickness of the disk drive.
This solution has proved still unsatisfactory, however. Should the thickness of disk drive be lessened to a greater extent than heretofore, the conductive pattern on tile circuit board for the upper transducer, mounted to the pivoted load arm, might come into contact with the metal made top cover of the disk drive.
An obvious remedy to this problem might be to provide some electrically insulating overlay on the circuit board or on the conductive pattern. The coating of an insulating paint would be one possible method to this end, but it would take too much cost and labor in consideration of coatings of constant, appropriate thickness required. The adhesion of insulating sheet or film would be another practicable method. However, such sheet or film would not only add to the weight of the circuit board but also impair the flexibility of the circuit board and, in consequence, the resiliency of the flexure seat. These inconveniences would be overcome if the small pieces of insulating sheet or film were attached to only those parts of the conductive pattern which might contact the top cover of the disk drive. This method is also objectionable in view of the cost and labor involved.
The applicant has also contemplated to cover with flexible overlays the complete surfaces of printed circuit boards having the conductive patterns formed thereon. Parts of the overlays may then be removed for exposing those parts of the conductive patterns to which the transducer overlays are to be soldered. An objection to this measure is that, flexible as they may be, the overlays would nevertheless lessen the flexibility of the circuit boards. The partial removal of the overlays would also be very troublesome.